Technologies, in particular, semiconductor technologies, make progresses day by day. Wafers are among the most important materials for semiconductor fabrication. The major raw material of wafers is silicon dioxide. Wafers are processed by steps including deposition, etching, annealing, photoresist, coating, and development. A wafer can give tens of even hundreds of integrated circuits, depending on its size. In order to fabricate wafers having various circuits and electronic devices, masks are required for planning and designing in advance.
Masks are molds for fabricating wafers. While fabricating integrated circuits, the design of the integrated circuits is first fabricated on masks. The fabrication of masks are designed and planned according to the circuit design. If the circuit design is more complicated and fine, more layers of masks are possibly required.
In order to use masks for planning and designing circuits on wafers, photolithography should be adopted. The technology makes use of the principle of exposure. When light passes through a mask and projects to a silicon wafer, specific patterns can be exposed and rebuilt on the wafer. After the development process, the mask pod can be cleaned and reused repeatedly.
Mask pods can be categorized into front- and top-opening types. The opening of mask pod is directional. Thereby, wile loading a mask pod to a lithography machine, attention should be paid to the orientation of the mask pod. Otherwise, the mask pad might be inoperative. Alternatively, if the loaded position is shifted, although the opening of the mask pod is not affected, the exposure position is shifted during the photolithography process.
For avoiding the above conditions, positioning mechanisms are provided in the photolithography machine according to some references. The positioning mechanism uses the mechanisms designed on the mask pods to match those designed on the machines. Thereby, the mask pods can be loaded in a specific orientation with respect to the photolithography machines.
In addition, sensing devices are adopted for sensing the loading locations of mask pods for ensuring the precise positioning of the mask pods. According to some references, sensors sense the existence of a wafer pod and send a signal. Barcode scanner acquires the signal from the sensor and reads the identification code of the wafer pod. In the references, while using the sensors, the detection of the sensors might be unstable owing to the smooth surface of the mask pod. As a consequence, the locations of the characteristic regions on the mask pod cannot be judged precisely.
The present invention mitigates the drawbacks in the references and provides an EUV mask pod having marks. One or more mark is produced using laser engraving. By ensuring the voltage value generated by the reflection light from the one or more mark, it is judged whether the one or more mark is corresponded to the processing machine. Thereby, the processing machine can detect precisely if the mask pod is located at the processing location.